Since the development of crude communication systems based on electrical signals, the world's appetite for more and more advanced forms of communication has continually increased. From wired cable networks over which operators would exchange messages using Morse-Code, to the broadband wireless networks of today, whenever technology has provided a means by which to communicate more information, people have found a use for that means, and have demanded more.
Modern communication networks are best characterized by features such as high bandwidth/data-rate, complex communication protocols, various transmission mediums, and various access means. Fiber optic networks span much of the world's surface, acting as long-haul networks for carrying tremendous amounts of data between distant points on the globe. Cable and other wire-based networks supplement coverage provided by fiber optic networks, where fiber networks have not yet been installed, and are still used as part of local area networks (“LAN”), for carrying data between points relatively close to one another. In addition to wire-based networks, wireless networks such as cellular networks (e.g. 2G, 3G, CDMA, WCDMA, WiFi, etc.) may be used to supplement coverage for various devices (e.g. cell phone, wireless IP phone, wireless internet appliance, etc.) not connected to a fixed network connection. Wireless networks may act as complete local loop networks and may provide a complete wireless solution, where a communication device in an area may transmit and receive data from another device entirely across the wireless network.
With the proliferation of communication networks and the world's growing reliance upon them, proper performance is crucial. High data rates and stable communication parameters at low power consumption levels are highly desirable for communication devices. However, degradation of signal-to-noise ratio (“SNR”) as well as bit energy to noise ratio (“Eb/No”) and interference ratios such as Carrier-to-Interference (“C/I”) ratio occur to a signal carried along a transmission medium (e.g. coax, unshielded conductor, wave guide, open air or even optical fiber or RF over fiber). This degradation and interferences may occur in TDMA, CSMA, CDMA, EVDO, WCDMA and WiFi networks respectively. Especially in the field of cellular communication, there has been a constant push for improved technologies intended to compensate for SNR degradation and to improve data rates and connection reliability.
3GPP LTE (Long Term Evolution) is the name given to a project within the Third Generation Partnership Project to improve the UMTS mobile phone standard to cope with future technology evolutions. Goals include improving spectral efficiency, lowering costs, improving services, making use of new spectrum and reframed spectrum opportunities, and better integration with other open standards. The LTE air interface will be added to the specification in Release 8 and can be found in the 36-series of the 3GPP specifications. Although an evolution of UMTS, the LTE air interface is a completely new systems based on OFDMA in the downlink and SC-FDMA (DFTS-FDMA) in the uplink that efficiently supports multi-antenna technologies (MIMO). The architecture that will result from this work is called EPS (Evolved Packet System) and comprises E-UTRAN (Evolved UTRAN) on the access side and EPC (Evolved Packet Core) on the core side.
Much of the 3GPP standard will be oriented around upgrading UMTS to a so-called fourth generation mobile communications technology, essentially a wireless broadband Internet system with voice and other services built on top.
The Standard Includes:
                Peak download rates of 326.4 Mbit/s for 4×4 antennas, 172.8 Mbit/s for 2×2 antennas for every 20 MHz of spectrum.        Peak upload rates of 86.4 Mbit/s for every 20 MHz of spectrum[2]        5 different terminal classes have been defined from a voice centric class up to a high end terminal that supports the peak data rates. All terminal will be able to process 20 MHz bandwidth.        At least 200 active users in every 5 MHz cell. (i.e., 200 active data clients)        Sub-5 ms latency for small IP packets        Increased spectrum flexibility, with spectrum slices as small as 1.5 MHz (and as large as 20 MHz) supported (W-CDMA requires 5 MHz slices, leading to some problems with roll-outs of the technology in countries where 5 MHz is a commonly allocated amount of spectrum, and is frequently already in use with legacy standards such as 2G GSM and cdmaOne.) Limiting sizes to 5 MHz also limited the amount of bandwidth per handset        Optimal cell size of 5 km, 30 km sizes with reasonable performance, and up to 100 km cell sizes supported with acceptable performance        Co-existence with legacy standards (users can transparently start a call or transfer of data in an area using an LTE standard, and, should coverage be unavailable, continue the operation without any action on their part using GSM/GPRS or W-CDMA-based UMTS or even 3GPP2 networks such as CDMA or EV-DO)        Supports MBSFN (Multicast Broadcast Single Frequency Network). This feature can deliver services such as Mobile TV using the LTE infrastructure, and is a competitor for DVB-H-based TV broadcast.        
Release 8's air interface, E-UTRA (Evolved UTRA, the E-prefix being common to the evolved equivalents of older UMTS components) may be used by UMTS operators deploying their own wireless networks. It's important to note that Release 8 is intended for use over any IP network, including WiMAX and WiFi, and even wired networks.
The proposed E-UTRA system uses OFDMA for the downlink (tower to handset) and Single Carrier FDMA (SC-FDMA) for the uplink and employs MIMO with up to four antennas per station. The channel coding scheme for transport blocks is turbo coding and a contention-free quadratic permutation polynomial (QPP) turbo code internal interleaver.
The use of OFDM, a system where the available spectrum is divided into thousands of very thin carriers, each on a different frequency, each carrying a part of the signal, enables E-UTRA to be much more flexible in its use of spectrum than the older CDMA based systems that dominated 3G. CDMA networks require large blocks of spectrum to be allocated to each carrier, to maintain high chip rates, and thus maximize efficiency. Building radios capable of coping with different chip rates (and spectrum bandwidths) is more complex than creating radios that only send and receive one size of carrier, so generally CDMA based systems standardize both. Standardizing on a fixed spectrum slice has consequences for the operators deploying the system: too narrow a spectrum slice would mean the efficiency and maximum bandwidth per handset suffers; too wide a spectrum slice, and there are deployment issues for operators short on spectrum. This became a major issue with the US roll-out of UMTS over W-CDMA, where W-CDMA's 5 MHz requirement often left no room in some markets for operators to co-deploy it with existing GSM standards.
OFDM has a link spectral efficiency greater than CDMA, and when combined with modulation formats such as 64QAM, and techniques as MIMO, E-UTRA has proven to be considerably more efficient than W-CDMA with HSDPA and HSUPA.
The subcarrier spacing in the OFDM downlink is 15 kHz and there is a maximum of 1200 subcarriers available. Number of subcarriers is dependent on the used bandwidth (1.4 MHz and up to 20 Mhz), subcarriers don't occupy 100% of the used bandwidth as Cyclic Prefixes (Guards) occupies a part of it. The Mobile devices must be capable of receiving all subcarriers but a base station need only support transmitting 72 subcarriers. The transmission is divided in time into time slots of duration 0.5 ms and subframes of duration 1.0 ms. A radio frame is 10 ms long.
Supported modulation formats on the downlink data channels are QPSK, 16QAM and 64QAM.
The currently proposed uplink uses SC-FDMA multiplexing, and QPSK or 16QAM (64QAM optional) modulation. SC-FDMA is used because it has a low Peak-to-Average Power Ratio (PAPR). Each mobile device has at least one transmitter. If virtual MIMO/Spatial division multiple access (SDMA) is introduced the data rate in the uplink direction can be increased depending on the number of antennas at the base station. With this technology more than one mobile can use the same resources.
Spectrum aggregation is considered in LTE-Advanced for supporting large system bandwidths. The basic idea is to aggregate multiple, non-contiguous spectral components—centered around different carriers—in order to form the desired full system bandwidth. This allows reusing existing spectral bands (e.g. those of UMTS or LTE Rel8, with bandwidths of 1.4-20 MHz each) within a single system, enlarging its total bandwidth and hence the peak rate per user.
The use of multiple subcarriers in downlinks and uplinks (herein after also referred to multi-carriers or multiple carriers) raises certain power control issues. Uplink power control (PC) is a very important ingredient in cellular systems, required for compensating for path-loss of signals transmitted by different users in the uplink. It is used for maintaining acceptable Interference-rise over Thermal levels (IoT), for achieving a desired QoS, and having a reliable control data channel. In the LTE cellular standard, the uplink PC is based on fractional power control. The path-loss is fractionally compensated depending on cell-specific parameters. These parameters are signaled by the eNode-B to the user equipment (“UE”) via higher layers (e.g. RRC), and additionally the eNode-B sends TPC commands at a higher rate for compensating the estimation errors of the UE measurements. The UE estimates the path-loss, and based on the PC parameters and the TPC commands adjusts its transmission power.
As data rates and service requirements for base station functionality increase, there has developed a trend for increasing the numbers of smaller base stations. Constraints in available space and the cost associated with deploying and operating large numbers of base stations is, however, a limiting factor. Therefore, there is a need for methods, circuits and systems for providing base station functionality at one or more nodes of a distributed data network.